The present invention relates to construction technologies. In particular, the present invention relates to the lifting and installation of elongated elements, or assemblies of elements, such as for example, steel columns, precast concrete columns, prefabricated reinforcing cages, and tower-like structures, to name a few. Examples of prefabricated reinforcing cages are shown in the patents Ferrer (U.S. Pat. No. 8,381,479), Hasak (U.S. Pat. No. 4,467,583) and Bongiorno (U.S. Pat. No. 9,267,287). Examples of tower-like structures are shown in the patents of Fang (U.S. Pat. No. 9,038,348) and Murata (U.S. Pat. No. 8,209,913). The present invention provides a method and apparatus for the safe, efficient and economical erection and installation of such elongated elements.
The current methods for erection of elongated, substantially vertically oriented, elements includes attaching lifting lines such as cables and slings from a lifting device such as a crane near the top of the element. This results in a condition where there is a pivot point at the top of the element, with the center of gravity of the element located below the pivot point. This results in a naturally stable condition such as a traditional pendulum. However, this also necessitates that the disconnection of the lifting lines after the element is installed at its intended location is to be made at the top of the element. In some cases, especially where the element is tall, it is difficult to access the upper portion of the element to disconnect the lifting lines. Doing so may also pose certain safety concerns.
Alternatively, others have attached the lifting lines to lower portions of elongated elements to overcome these concerns. However, this results in a condition where the pivot point is located below the center of gravity of the element. This results in a naturally unstable condition, such as the case of an inverted pendulum. See FIGS. 26A-27B for diagrammatic illustration.
It is therefore advantageous to have an erection method where the connection point of the lifting lines to an elongated, substantially vertical, element is at a lower point where the connection is safer and more easily accessible to disconnect them, while at the same time providing lateral stability to the element.